<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        const PI=3.1415926
        let R=prompt("请输入圆的半径：")
        let C=2*PI*R
        let S=PI*R*R
        document.write("圆的周长为：",C)
        document.write("圆的面积为：",S)

        console.log('ZS'-2);
        console.log(NaN-2);
    </script>
</body>
</html>